The present invention relates to an ultrasonic microscope, especially to a mechanism for detachably attaching an ultrasonic head to a vibration shaft of a vibrator.
Usually, in case of displaying an ultrasonic image of a specimen by means of the ultrasonic microscope, use is made of a two-dimensional scanning such that the vibration shaft of the vibrator to which is secured the ultrasonic head having a piezoelectric transducer is vibrated at a high speed in X direction so as to effect a main-scanning, while a specimen stage on which the specimen is placed is moved at a low speed in Y direction to effect a sub-scanning. In the known vibrator, as shown in FIG. 1, an ultrasonic head 1 comprising an acoustic lens and a piezoelectric transducer is secured to an arm 2 and the arm 2 is connected to one end of a vibration shaft 3 of the vibrator. The other end of the vibration shaft 3 is connected to a bobbin of a voice coil 7 wounded between a yoke 5 and a pole-piece 6 so as to cross a magnetic field generated by a magnetic circuit consisting of a magnet 4, the yoke 5 and the pole-piece 6, and is movably supported by a leaf spring 8 in a direction perpendicular to an ultrasonic wave emitting direction from the ultrasonic head 1 i.e. an axial direction of the voice coil 7. It is possible to vibrate the ultrasonic head 1 in X direction by supplying a predetermined alternating current to the voice coil 7.
In the known ultrasonic microscope mentioned above, in order to vary or change a frequency of the ultrasonic wave so as to vary a resolution of the image, it is necessary to exchange the ultrasonic head 1 by another ultrasonic head. In this case, the ultrasonic head 1 is fixedly secured to the arm 2 and this arm 2 is detachably secured to the vibration shaft 3 by means of screws 9. Therefore, there is a drawback that a troublesome work is required every time the ultrasonic head 1 is exchanged. In addition, a radio-frequency (R.F.) cable 10, i.e. a high-frequency coaxial cable is connected to the piezoelectric transducer of the ultrasonic head 1. Therefore, the influence of the R.F. cable 10 upon the vibrator is varied due to the position and the characteristics of the R.F. cable, so that the ultrasonic head 1 cannot be moved linearly at a constant speed within a range of the vibration and thus there is a drawback that the ultrasonic image having high resolution cannot be obtained. These drawbacks occur particularly when the large scanning region obtained by making the range of the vibration large is required.